The present invention relates to electrical diodes and in particular to high-speed tunnel diodes having low capacitance.
Diodes are two-terminal electrical devices that block electrical current in one direction and allow it to flow in the opposite direction. This rectification property is often used in electrical circuits to extract a direct current from an alternating current source either for power generation or demodulation.
Typical solid-state diodes (to be distinguished from vacuum tube diodes, for example) employ a junction of different materials that provides a nonlinear and asymmetric IV-curve (current plotted as a function of voltage) across the diode. Common pn-diodes employ a junction between specially doped semiconductors and provide a forward voltage drop, in the conducting direction, of between 0.7-1.7 V. Schottky diodes provide a lower forward voltage drop of approximately 0.15-0.45 V using a junction between a metal and a doped semiconductor. Metal-insulator-metal (MIM) tunnel diodes, in contrast, provide two metal terminals separated by an insulating layer, the latter is traversed by electrons through quantum tunneling. MIM diodes potentially can operate in the terahertz region because of the higher speed of tunneling in contrast to carrier transport through a depletion region in normal junction diodes.
In part because of their high operating frequency, MIM diodes are potential candidates for rectennas, that is, antennas that provide for power rectification as the receiving device for wireless transmission of power through microwave transmission. MIM diodes have also been considered for use with so-called “nantennas” which are intended to employ similar principles to that of the rectenna for the conversion of light to electrical energy.